Commercial Carbon Dioxide Uses: Carbon Dioxide Enhanced Oil Recovery

Carbon Dioxide Market
The Global CCS Institute1 has reported on market demand for carbon dioxide (CO2). In 2011, the global demand for CO2 was estimated at 80Mtpa, of which:

50Mtpa is utilized for Enhanced Oil Recovery, almost exclusively in North America, and

the remaining 30Mtpa represents the global demand of all other uses, predominantly the mature industries of beverage carbonation and food industry uses.

The breakdown is shown in Figure 1.

Figure 1: Approximate proportion of current CO2 demand by end use

CO2 for beverage carbonation and food industry must meet stringent standards of purity; therefore it is usually obtained from sources such as corn-to-ethanol plants, breweries, etc. Otherwise, commercially-produced carbon dioxide is recovered from CO2-producing wells, and hydrogen, synthetic natural gas, or ammonia production plants using natural gas, coal, or other hydrocarbon feedstocks.

Carbon Dioxide Enhanced Oil Recovery
By far the most extensive use of CO2 in the United States is for enhanced oil recovery. Carbon dioxide enhanced oil recovery (CO2 EOR) is a technique used to recover oil, typically from mature fields that have ceased being productive through traditional primary and secondary recovery methods. Primary and secondary recovery methods typically leave two-thirds of the original oil in place (OOIP). To put the potential of EOR into perspective, of the total of 600 billion barrels of oil that have been discovered in the United States, approximately 400 billion barrels are unrecoverable by conventional methods. Half of that unrecoverable oil (200 billion barrels) is at reasonable depths at which EOR may be applicable.

CO2 EOR is an established technique in the United States, and is the only oil recovery technique that has shown any growth since the 1980s. In fact, CO2 EOR now accounts for over 5% of the Nation's oil production. It can extend the productive life of an existing oilfield by several decades, and it can lead to recovery of millions of barrels of additional oil.

The basic principle behind CO2 EOR is the mutual solubility of crude oil and CO2 in the temperature and pressure conditions of a geologic reservoir. Given the right conditions, injected CO2 is able to dissolve and displace oil residue that is trapped in rock pores (like a solvent is able to displace grease from a dirty bicycle chain). In a typical CO2 flood operation, a pipeline delivers CO2 to the oilfield, where it is directed to injection wells. These wells are strategically placed to optimize the areal sweep of the CO2 through the reservoir. As the injected CO2 moves through pore spaces in the rock, it encounters residual crude oil. The crude oil mixes with the CO2, decreases oil viscosity, pressurizes it, and mobilizes it, forming a concentrated oil bank that is swept to producing wells. In this way, oil and gas companies are able to gain access to oil that would otherwise be left in the ground.

CO2 EOR in Carbon Capture and Storage (CCS)

CO2 EOR is additionally attractive because of its effectiveness and its ability to sequester gasification-created CO2 emissions. Following CO2 EOR operations, the CO2 can remain underground in the reservoir, and is thereby prevented from entering the atmosphere. The U.S. Department of Energy has significantly funded and supported CCS projects in the United States, resulting in the most robust portfolio of large-scale CCS projects in the world. Figure 2 shows large-scale projects in North America; 17 of the 19 projects in the U.S. include CO2 EOR as the preferred storage type (the two others involve CO2 storage in saline formations).

Background on CO2 EOR
CO2 EOR was first tested in the early 1970s in West Texas. Since then, it has been utilized successfully throughout the Permian Basin of West Texas and eastern New Mexico. It is currently being used in oilfields in Kansas, Mississippi, Wyoming, Oklahoma, Colorado, Utah, Montana, Alaska, and Pennsylvania. In the United States CO2 EOR production has increased to over 300,000 barrels of oil per day2. It is estimated that we have the potential to produce about 21.4 billion barrels of additional oil using current best practices, but using "next generation" CO2 EOR technologies underdevelopment, the economically recoverable oil from existing domestic fields in the lower 48 states would increase to 63.3 billion barrels using advanced techniques.3

Industrially-Sourced CO2
Until recently, most CO2 EOR has depended on naturally-occurring underground deposits as the source of the CO2. In recent years, however, industry has begun to utilize CO2 that has been captured as a by-product of fossil fuel combustion, gasification, or other industrial processes. Because a ton of CO2 costs up to $30 delivered, and each ton can yield 2-3 barrels of oil, there is a strong economic incentive to re-use industrially-sourced CO2 from gasification plants, gas processing facilities, and power generation plants.

Benefits
CO2 EOR represents a win-win strategy for beneficial use of industrially-sourced CO2. From an economic standpoint, CO2 EOR is a highly effective tool for re-invigorating oil production from mature fields that might otherwise be abandoned. From an environmental standpoint, it represents a practical way to recycle and utilize CO2 while reducing overall atmospheric CO2 emissions.